EP2242824B1 - Use of lubricant compositions for transmissions - Google Patents

Description

Field of the invention

The present invention relates to the use of lubricating compositions for transmissions in the field of motor vehicles, more particularly adapted to the lubrication of bridges, having the property of increasing the fatigue resistance of the bridge gears.

Technological Background of the Invention

A typical cause of damage to bridge gears is fatigue damage, which occurs under repeated forces. This phenomenon is induced by repeated rolling constraints under heavy loads.

This results in phenomena of pitting (superficial fatigue) or peeling (deep fatigue). Chipping occurs after a long time of aging, preceding visible deterioration. The mechanisms are poorly known, but the phenomenon starts with the initiation of cracks to a certain depth below the surface, these cracks propagate, and when normal cracks on the surface are created, scales break off abruptly.

The phenomenon of flaking is particularly noticeable on heavy goods vehicles, where the gears are subjected to very heavy loads and very long durations of use.

The prevention of this phenomenon involves a reduction of contact stresses thanks to an appropriate geometry of the parts, and the reduction of friction, avoiding adhesion.

Lubricant is involved in this prevention process, due to its viscosity and the physicochemical reactivity of its additives.

Sulfur additives, as well as phosphorus and phospho-sulfur additives, are widely used in bridges and gearbox oil formulations as anti-wear and extreme pressure additives. They protect the friction parts under heavy load by forming a film adsorbed on their surface.

Sulfurized additives, forming a tribo iron sulphide film of low shear strength, easily peelable, make it possible in particular to avoid galling, a phenomenon which occurs at the first stages of use, when the resistance of the interface exceeds that of the underlying material.

The additives present in the lubricant can also have an impact, positive or negative, on the propagation of cracks inside the parts and thus on the phenomenon of chipping. The request for US Patent 5,942,470 discloses lubricating oil compositions for cans. There is therefore a need to increase the service life of friction parts, in particular bridge gears, by limiting the appearance of the peeling phenomenon.

Summary of the invention.

To this end, the present invention proposes to improve the spall protection properties of transmission lubricating compositions containing sulfur and phosphosulfur compounds comprising a step of adding, in the lubricating composition for initial transmission, compounds (c) reducing by at least 5% the mass content of active sulfur measured by ASTM D1662 in the final composition.

Preferably, according to the invention, the ratio between the final Sfinal sulfur content in the final composition, after implementation of the process, and the initial Sinitial sulfur mass content in the initial composition, before carrying out the process, mass content measured according to ASTM D2622, Sfinal / Sinitial is greater than or equal to 1.05.

• le rapport entre la teneur massique en Soufre actif à 150°C, mesurée selon la norme ASTM D1662, et la teneur massique en élément Soufre, mesurée selon la norme ASTM D5185, Sactif/S, est inférieure à 0,45 et,
• la teneur massique en élément soufre, mesurée selon la norme ASTM D5185, est supérieure à 20 %, préférentiellement supérieure à 40 %.

Selon l'invention l'additif (c) est choisi parmi une ou plusieurs oléfines soufrées répondant à la formule générale R1-Sx-R2, où R1 et R2 sont des groupes alkyl comportant de 3 à 15 atomes de carbone, préférentiellement de 1 à 5 atomes de carbone, préférentiellement 3 atomes de carbone, et x est un entier compris entre 2 et 6, préférentiellement égal à 3.Preferably, according to the invention, the added compound (c) is a sulfur additive in which:

• the ratio between the active sulfur content at 150 ° C., measured according to ASTM D1662, and the sulfur element mass content, measured according to ASTM D5185, Sactif / S, is less than 0.45 and,
• the mass content of sulfur element, measured according to ASTM D5185, is greater than 20%, preferably greater than 40%.

According to the invention, the additive (c) is chosen from one or more sulfurized olefins corresponding to the general formula R 1 -Sx-R 2, where R 1 and R 2 are alkyl groups containing from 3 to 15 carbon atoms, preferably from 1 to 5 carbon atoms, preferably 3 carbon atoms, and x is an integer between 2 and 6, preferably equal to 3.

1. (a) de 60 à 90 % en poids d'une ou plusieurs huiles de base, d'origine minérale, synthétique, ou naturelle,
2. (b) au moins un additif phosphoré ou phospho-soufré anti-usure et extrême pression,
3. (c) 0,1 à 2% en poids d'au moins moins un additif soufré anti-usure et extrême pression telle que défini dans la revendication 1 dans laquelle :
   • le rapport entre la teneur massique en élément soufre, mesurée selon la norme ASTM D2622, et la teneur massique en élément Phosphore, mesuré selon la norme ASTM D5185, ,, de ladite composition lubrifiante, est compris entre 20 et 40 de préférence entre 25 et 35 ;
   • le rapport entre la teneur massique en Soufre actif à 150°C, mesurée selon la norme ASTM D1662, et la teneur massique en élément Soufre, mesurée selon la norme ASTM D5185, Sactif/S, de ladite composition lubrifiante, est inférieur à 0,34, préférentiellement inférieur à 0,33.

Preferably, according to the invention, the final lubricating composition comprises:

1. (a) from 60 to 90% by weight of one or more base oils, of mineral, synthetic or natural origin,
2. (b) at least one phosphorus or phospho-sulfur additive, anti-wear and extreme pressure,
3. (c) 0.1 to 2% by weight of at least one anti-wear and extreme pressure sulfur additive as defined in claim 1 wherein:
   • the ratio of the sulfur element mass content, measured according to the standard ASTM D2622, and the mass content of Phosphorus element, measured according to ASTM D5185, of said lubricating composition, is between 20 and 40, preferably between 25 and 35;
   • the ratio between the active sulfur content at 150 ° C., measured according to ASTM D1662, and the sulfur element mass content, measured according to ASTM D5185, Sactif / S, of said lubricating composition, is less than 0, 34, preferentially less than 0.33.

• le rapport entre la teneur massique en Soufre actif à 150°C, mesurée selon la norme ASTM D1662, et la teneur massique en élément Soufre, mesurée selon la norme ASTM D5185, Sactif/S, est inférieure à 0,45 et,
• la teneur massique en élément soufre, mesurée selon la norme ASTM D5185, est supérieure à 20 %, préférentiellement supérieure à 40 %.

Selon l'invention, l'additif (c) est choisi parmi d'une ou plusieurs oléfines soufrées répondant à la formule générale R1-Sx-R2, où R1 et R2 sont des groupes alkyl comportant de 3 à 15 atomes de carbone, préférentiellement de 1 à 5 atomes de carbone, préférentiellement 3 atomes de carbone, et x est un entier compris entre 2 et 6, préférentiellement égal à 3.Preferably, according to the invention, the mass content of active sulfur at 150 ° C, Sactif, measured according to ASTM D1662 is less than or equal to 1,200%, preferably less than or equal to 1,180%. The lubricant composition used according to the invention contains from 0.1 to 2% by weight of at least one sulfur additive (c) in which:

• the ratio between the active sulfur content at 150 ° C., measured according to ASTM D1662, and the sulfur element mass content, measured according to ASTM D5185, Sactif / S , is less than 0.45 and,
• the mass content of sulfur element, measured according to ASTM D5185, is greater than 20%, preferably greater than 40%.

According to the invention, the additive (c) is chosen from one or more sulfur-containing olefins corresponding to the general formula R 1 -S x -R 2, where R 1 and R 2 are alkyl groups containing from 3 to 15 carbon atoms, preferentially from 1 to 5 carbon atoms, preferably 3 carbon atoms, and x is an integer between 2 and 6, preferably equal to 3.

Preferably, the lubricating composition used according to the invention comprises, as base oil (a), from 10% to 20% of one or more Group V base oils, optionally in combination with one or more oils. from API groups I, II, III, IV or VI and / or naturally occurring base oils.

• 20 à 30 % en poids par rapport au poids total de lubrifiant, d'une huile de base paraffinique de forte viscosité, appartenant au groupe I de la classification API, de viscosité comprise entre 30 et 34 Cst à 100 °C (25,5 % BSS)
• 30 à 45 % en poids, par rapport au poids total de lubrifiant, d'une huile de base paraffinique du groupe I de viscosité comprise entre 10 et 15 Cst à 100 °C (40,35% 600NS)
• 10 à 20 % en poids, par rapport au poids total de lubrifiant, d'une huile synthétique du groupe V.

Preferably, according to the invention, the 60 to 90% of base oil (a) consist of:

• 20 to 30% by weight, relative to the total weight of lubricant, of a paraffinic base oil of high viscosity, belonging to group I of the API classification, with a viscosity of between 30 and 34 Cst at 100 ° C. (25.5%). % BSS)
• 30 to 45% by weight, based on the total weight of lubricant, of a Group I paraffinic base oil with a viscosity of between 10 and 15 Cst at 100 ° C. (40.35% 600NS)
• 10 to 20% by weight, based on the total weight of lubricant, of a Group V synthetic oil.

Preferably, according to the invention, the phosphorus or phospho sulfur-containing additive (s) anti-wear and extreme pressure (b) are chosen from alkyl phosphates, alkyl phosphonates, thiophosphoric acid, thiophosphorous acid, esters and the like. of these acids, their salts, alkyl dithiophosphates.

Preferably, the composition used according to the invention has a Brookfield dynamic viscosity of less than or equal to 150 mPa at temperatures greater than or equal to -12 ° C., preferably greater than or equal to -26 ° C., preferably greater than or equal to 40 ° C.

Preferably, the composition used according to the invention, has a kinematic viscosity at 100 ° C is less than or equal to 32.5 Cst.

Preferably, the composition used according to the invention belongs to the class of multigrade oils of grade 85W140, 85W90, 80W90, or 75W90 or monograde oils of grade 140 or 90 according to the standard SAEJ306. A lubricant composition according to the invention is used as a lubricant to increase the resistance to spalling of metal parts in friction, preferably the gears of vehicle decks.

Surprisingly, the Applicant has found that it is possible to improve the spall protection properties of brine oil formulations containing conventional phosphorus-sulfur and / or phosphorus compounds, by the addition of certain reducing compounds from less than 5%, preferably at least 8% to 20% the active sulfur content of said formulations.

This is all the more surprising since these compounds may themselves contain sulfur and active sulfur. Without wishing to be bound by any theory, these compounds seem to "absorb" or "stabilize" a portion of the active sulfur initially present in the lubricant compositions before treatment.

The present invention also relates to the use of lubricating compositions for increasing the service life of friction parts, including bridge gears, by limiting the occurrence of peeling phenomenon.

Surprisingly, the Applicant has found that certain transmission oils having a specific ratio between their mass content of sulfur element and phosphorus element, S / P, as well as between their mass content of active sulfur and sulfur, Sactif / S , allows to considerably increase (up to double) the life of the parts.

The active sulfur content of a compound or lubricating composition is understood to mean the sulfur consumed to form copper sulphide upon the addition of copper powder at 150 ° C. in said compound or said lubricating composition. The mass% of active sulfur is measured by the ASTM1662 standard.

Thus, these properties for improving peeling resistance can for example be obtained by introducing certain sulfur-type olefins. dialkylsulphide, in a bridges oil formula containing conventional phosphorus-sulfur and / or phosphorus compounds, and optionally conventional sulfur-containing additives.

DETAILED DESCRIPTION OF THE EMBODIMENTS OF THE INVENTION Basic oils:

The base oils used according to the invention may be of mineral, synthetic or natural origin.

The mineral base oils used according to the invention include all types of bases obtained by atmospheric distillation and vacuum of crude oil, followed by refining operations such as solvent extraction, desalphating, solvent dewaxing, hydrotreatment, hydrocracking and hydroisomerization. , hydrofinishing, ...

The preferred mineral base oils are Group I oils according to the API classification, obtained by solvent extraction and solvent dewaxing of an atmospheric residue, deasphalted oil, etc.

In particular, the lubricant compositions used according to the present invention advantageously comprise from 20 to 30% by weight of a paraffinic base oil of high viscosity of group I according to the API classification, with a viscosity of between 30 and 34 Cst at 100 ° C. and from 30 to 45% by weight of a Group I paraffinic base oil having a viscosity of 10 to 15 Cst at 100 ° C.

The synthetic base oils used according to the present invention are oils belonging to groups IV, V and VI of the API classification, including polyalphaolefins, polyinternal olefins, alkyl aromatics, alkyl benzene, alkylnaphthalenes, esters, diesters, polyol esters such as pentaerythritol esters, oligomers of aplhaolefins and esters, polyalkylene glycols.

In particular, the lubricant compositions used according to the present invention advantageously comprise from 10 to 20% by weight of a Group V synthetic base oil, in particular ester-type bases, in optional combination with one or more selected base oils. among groups I, II, III, IV or VI of the API classification, and / or base oils of natural origin.

The preferred Group V synthetic base oils are the diesters such as ditridecyl glutarate, di 2 ethyl hexyl adipate, di isodecyl adipate, ditridecyl adipate, di 2 ethyl hexyl cebacate.

• 20 à 30 % en poids par rapport au poids total de lubrifiant, d'une huile de base paraffinique de forte viscosité, appartenant au groupe I de la classification API, de viscosité comprise entre 30 et 34 Cst à 100 °C (25,5 % BSS)
• 30 à 45 % en poids, par rapport au poids total de lubrifiant, d'une huile de base paraffinique du groupe I de viscosité comprise entre 10 et 15 Cst à 100 °C (40,35 % 600NS)
• 10 à 20 % en poids, par rapport au poids total de lubrifiant, d'une huile synthétique du groupe V, par exemple une huile de base de type ester.

Thus, the lubricant compositions used according to the present invention may advantageously comprise:

• 20 to 30% by weight, based on the total weight of lubricant, of a base oil paraffinic compound of high viscosity, belonging to group I of the API classification, with a viscosity of between 30 and 34 Cst at 100 ° C (25.5% BSS)
• 30 to 45% by weight, based on the total weight of lubricant, of a Group I paraffinic base oil with a viscosity of between 10 and 15 Cst at 100 ° C. (40.35% 600NS)
• 10 to 20% by weight, based on the total weight of lubricant, of a Group V synthetic oil, for example an ester base oil.

Anti wear and extreme pressure additives:

The phospho-sulfur antiwear and extreme pressure additives used in the present invention are, for example and not exclusively, thiophosphoric acid, thiophosphorous acid, esters of these acids, their salts, and dithiophosphates, particularly zinc dithiophosphates.

Examples which may be mentioned as examples of phospho-sulfur-containing anti-wear and extreme pressure additives are those containing from 1 to 3 sulfur atoms, such as monobutylthiophosphate, monooctylthiophosphate, monolaurylthiophosphate, dibutylthiophosphate, dilaurylthiophosphate, tributylthiophosphate, trioctylthiophosphate, triphenylthiophosphate, trilaurylthiophosphate, monobutylthiophosphite, monooctylthiophosphite, monolaurylthiophosphite, dibutylthiophosphite, dilaurylthiophosphite, tributylthiophosphite, trioctylthiophosphite, triphenylthiophosphite, trilaurylthiophosphite and their salts.

Examples of salts of thiophosphoric acid esters and thiophosphorous acid are those obtained by reaction with a nitrogen compound such as ammonia or an amine or zinc oxide or zinc chloride.

The lubricating compositions used according to the present invention may also contain phosphorus anti-wear and extreme pressure additives, such as, for example, alkyl phosphates or alkyl phosphonates, phosphoric acid, phopsphorous acid and triesters of phosphorous acid and phosphoric acid, and their salts

Examples of sulfur anti-wear and extreme pressure additives include dithiocarbamates, thiadiazoles and benzothiazoles, sulfur-containing olefins.

The most common sulfur-containing olefins are still referred to as SIBs for "Sulfurized IsoButylenes".

These sulfur-containing olefins are generally obtained by a reaction for the sulfurization of olefins with sulfur, hydrogen sulphide or hydrated alkali metal sulphides, for example sodium sulphide. An example of processes for the preparation of such sulfurized olefins is for example described in US Pat. US 4344854 and US 5135670 .

A very wide range of olefins can be so sulphured. Preferentially, sulphurized olefins are manufactured from isobutylene, diisobutylene, triisobutylene, tripropylene, or tetrapropylene.

The SIBs thus produced are mixtures of compounds of poorly defined structure, including, among other impurities, trithiones, dithiolethiones and halogens, and a high content of active sulfur.

Sulfurized olefins used in the invention:

The sulfurized olefins used in the compositions according to the present invention are dialkyl sulfides represented by the formula R1-Sx-R2, or R1 and R2 are alkyl groups having a carbon number of between 3 and 15, and where x is an integer between 2 and 6.

The average size of the alkyl groups R 1 and R 2 can be obtained by NMR analysis. It can also be directly deduced from the nature of the olefins used as starting material.

The mass sulfur content of these products, measured by ASTM D 2622, then makes it possible to calculate the value of x.

These products are also characterized by their mass content of active sulfur, that is to say the sulfur released when the product is in the presence of copper. The quantity of copper sulphide formed is then measured. The free sulfur content at 150 ° C is measured according to ASTM D-1662.

The alkyl compounds of the dialkyl sulfides used according to the invention comprise from 3 to 15 carbon atoms, preferably from 3 to 12 carbon atoms.

Among the dialkyl sulphides used according to the invention, the short-chain compounds will advantageously be chosen (average number of carbon atoms of between 3 and 5, preferably of 4).

Dialkyl trisulfides (x = 3) will be preferred.

The sulfurized olefins used according to the invention preferably have a high content of sulfur element (greater than 20%, preferably greater than 40%) and are compounds in which the ratio between the active sulfur content by mass at 150 ° C., measured according to ASTM D1662, and the sulfur element mass content, measured according to ASTM D5185, Sactif / S, is less than 0.45.

These specific sulfur-containing olefins which are distinguished from the SIBS described above or in the patents US 4344854 and US 5135670 are for example obtained by reaction of hydrogen sulphide with isobutylene in the presence of catalyst.

Typically, the sulfurized olefins used in the invention are obtained from isobutylene, sulfur and hydrogen sulphide, by catalytic processes using solid catalysts such as those described in US Pat. EP 1149813 , US6544963 or by methods as described in US Pat. FR 2,607,496 and FR2 630 104 comprising reacting a mercaptan and sulfur in the presence of a basic catalyst. They can also be produced by a two-step process as described in the patent EP 342 454 firstly synthesizing a mercaptan from olefin and H 2 S in the presence of a solid catalyst and then thereafter bringing said mercaptan with sulfur and another heterogeneous calyser to form the olefin sulfur.

These processes lead to purer products, of better defined structure, having a higher sulfur content and a lower active sulfur content than the commonly used SIBs.

The sulfur-containing olefins mentioned above may also be advantageously used in combination with conventional SIBS as described above.

In the lubricating compositions for transmissions, the sulfur content of the base oil or of the base oil mixture, as well as the respective amounts of phospho sulfur, phosphorus and sulfur-containing extreme pressure additives, in particular sulfur-containing olefins, are generally chosen so that said compositions have a ratio between their sulfur element content, measured by the ASTM D4294 standard and their phosphorus element content, measured by the ASTM D5185 standard, ie S / P, or between 10 and 60. The lubricant compositions according to the present invention have a S / P ratio preferably between 20 and 40, preferably between 25 and 35.

• Outre les oléfines soufrées spécifiques décrites ci-dessus pour améliorer les propriétés de protection contre l'écaillage de compositions lubrifiantes contenant des additifs soufrés et phosphosoufrés, on peut ajouter des composés tels que les corps gras naturels insaturés, par exemple acide oléique, acide linoléique, acide stéarique ou bien des huiles naturelles contenant ces corps gras naturels insaturés seuls ou en mélange, telles que par exemple l'huile de colza, de tournesol, de palme, coprah, coco, huile de lin ou huile de ricin...ou bien des oléfines comme par exemple isobutylène, hexène, nonène, décène, dodecène, tetradecène, styrène,... Ces composés peuvent être utilisés seuls ou en mélange, en combinaison éventuelle avec les oléfines soufrées spécifiques décrites plus haut, dans les procédés d'amélioration des propriétés de protection contre l'écaillage de compositions pour transmissions contenant des composés soufrés et phospho soufré.

Other compounds imparting improved lubricating properties to the lubricating compositions

• In addition to the specific sulfur-containing olefins described above for improving the peel protection properties of lubricating compositions containing sulfur and phosphosulfur additives, compounds such as unsaturated natural fatty substances, for example oleic acid, linoleic acid, can be added. stearic acid or natural oils containing these unsaturated natural fats alone or in a mixture, such as for example rapeseed oil, sunflower, palm, coconut, coconut, linseed oil or castor oil ... or olefins such as isobutylene, hexene, nonene, decene, dodecene, tetradecene, styrene, etc. These compounds can be used alone or in admixture, optionally in combination with the specific sulfur-containing olefins described above, in processes for improving the chipping protection properties of transmission compositions containing sulfur and phospho-sulfur compounds.

• un rapport entre la teneur massique en élément soufre, mesurée selon la norme ASTM D2622, et la teneur massique en élément Phosphore, mesuré selon la norme ASTM D5185, S/P, de ladite composition lubrifiante, est compris entre 20 et 40, de préférence entre 25 et 35, et
• un rapport entre la teneur massique en Soufre actif à 150°C, mesurée selon la norme ASTM D1662, et la teneur massique en élément Soufre, mesurée selon la norme ASTM D5185, Sactif/S, de ladite composition lubrifiante, est inférieur à 0,33.

Preferably, the nature and the quantity of these additives is chosen so that the final composition, after implementation of the process, has the following characteristics:

• a ratio between the sulfur element mass content, measured according to ASTM D2622, and the phosphorus element mass content, measured according to ASTM D5185, S / P, of said lubricating composition, is between 20 and 40, preferably between 25 and 35, and
• a ratio between the active sulfur content by mass at 150 ° C., measured according to the ASTM D1662 standard, and the sulfur element mass content, measured according to ASTM D5185, Sactif / S, of said lubricating composition, is less than 0, 33.

Other additives:

The lubricant compositions used according to the present invention may also contain any type of additive adapted to their use.

Preferably, the total% by weight of phosphosulfur, phosphorus and sulfur-containing additives is between 10 and 30%.

Thickeners:

In particular, the compositions used according to the invention may contain one or more thickening additives whose role is to increase the viscosity of the composition, hot or cold, or improving viscosity index (VI) improvers.

These additives are most often polymers of low molecular weight, of the order of 2000 to 50 000 dalton (Mn).

They will preferably be present in an amount of 1 to 10% by weight in the compositions used according to the invention.

They may be chosen from PIBs (of the order of 2000 daltons), polyacrylate or poly methacrylates (of the order of 30000 daltons), olefin-copolymers, olefin and alpha olefin copolymers, EPDM, polybutenes Poly-alphaolefins with high molecular weight (viscosity 100 ° C.> 150), styrene-olefin copolymers, hydrogenated or not, etc.

Pour point depressor:

The compositions used according to the invention may contain one or more additives of a pour point depressant additive.

These additives may typically be present at from 0.1 to 2% by weight. It may be, for example, poly-Acrylates, Ethyl-Vinyl Acetates, ethylenic copolymers, condensation derivatives of naphthalene, ......

Anti-corrosion agents and copper passivating agents, for example such as polyisobutene succinic anhydrides, sulfonates thiadiazoles, mercaptobenzothiazole.

• des détergents tels que par exemple les sulfonates, phénates, salycilates de Calcium, Sodium, Magnésium, Barium, ...
• des dispersants comme les dérivés de Poly Iso butylène succinic anhydride, ...
• des antioxydants, qui peuvent être par exemple Antioxydants Aminés (Ocatadiphénylamines, Phényl-Alpha-Naphtyl Amines, ...), Phénoliques (BHT et dérivés), Soufrés (Phéntaes Sulfurisés), ...

The oils used according to the invention may also contain all types of additives suitable for their use, and in particular:

• detergents such as, for example, sulphonates, phenates, calcium salycilates, sodium, magnesium, barium, etc.
• dispersants such as polyisobutylene succinic anhydride derivatives, ...
• antioxidants, which may be for example Amino antioxidants (Ocatadiphenylamines, Phenyl-Alpha-Naphtyl Amines, ...), Phenolics (BHT and derivatives), Sulfurized (Phentaes Sulfurized), ...

The viscosity of the oils used according to the invention can be defined by their grade according to SAE J306. The viscosity values corresponding to the different grades are reported in Table 1 below.

The kinematic viscosity values at 100 ° C are measured according to the standard:
Brookfield viscosity measurements are made according to the standard: Table 1. Grade Brookfield 150,000 mPa.s KV 100 ° C, Cst max min max 70 W - 55 ° C 75 W - 40 ° C 80W - 26 ° C 85 W - 12 ° C 80 7 <11 85 11 <13.5 90 13.5 <18.5 110 18.5 <24 140 24 <32.5 190 32.5 <41 250 > 41

The oils used according to the invention preferentially have grades characteristic of bridge oil formulations for light or heavy vehicles. They are preferably grade 75W-90, 80W-90, 85W-90, 85W140, or monograde oils 90 or 140.

Examples:

Of course, the present invention is not limited to the examples and to the embodiment described and shown, but it is capable of numerous variants accessible to those skilled in the art.

The reference lubricant composition (A) is an 80W90 grade oil. This reference as well as compositions B, C, and D were prepared from a mixture of several base oils and additives.

The phosphosulfur additives are provided by a package of performance additive for transmission oils, providing all the basic properties (anti-wear, extreme-pressure, anti-oxidant, anti-corrosion, etc.), and in particular containing alkyl dithiophosphates, alkyl phosphonates, alkyl phosphates.

The characteristics of the sulfurized olefins OS1, OS2, OS3, respectively used in Examples B, C and D, are summarized in Table 2. Table 2 description DialkylTrisulfide OS1 Dialkylpentasulfide OS2 DialkylTrisulfide OS3 Number of carbon atoms of alkyl compounds (R1, R2) C12 C12 C4 Sulfur content (% by weight) ASTM D2622 21.5 30.5 44 Active sulfur at 150 ° C (% by weight) ASTM D 1662 4 23 18 Kinematic viscosity at 40 ° C (KV 40 ° C), Cst 53 164 5 PM Flash Point 139 139 114 Pour point <-20 ° C <-20 ° C <+ 10 ° C S active / S 0.18 0.75 0.40

The amounts of sulfur-containing olefins added to the reference to obtain the oils B, C and D were calculated so that the contribution of sulfur element is the same in the 3 examples B, C and D (a contribution of 0.2% by weight of S).

The mass compositions and the main characteristics of the oils A, B, C and D are given in table 3.

The mass content of phosphorus (ASTMD5185), sulfur (ASTM D2622), and active sulfur at 150 ° C (ASTM D1662) was measured for reference A and oils B, C, and D.

The theoretical sulfur and active sulfur contents were also calculated for the oils B, C, and D, knowing the content of the reference A (initial S, initial Sactif), and the quantities contributed by the compounds OS1, OS2, OS3. . Table 3. formulas reference except invention invention invention AT VS B D Viscous base Group I 25.50 25.34 25.25 25.38 Medium Base Group I 40.35 40,10 39.95 40.17 Group V synthesis base (ester) 15,00 14.91 14.85 14.93 Poly Iso Butene 5.50 5.47 5.45 5.47 Package of phospho-sulfur additives (Hitec 389) 13.25 13.17 13,12 13,19 polyacrylate 0.40 0.40 0.40 0.40 Dialkyl Trisulfide X = 3, C12, OS1, 1.00 Dialkyl Pentasulfide X = 5, C12, OS2, 0.63 Dialkyl Trisulfide X = 3, C4, OS3, 0.46 P (mg / kg) ASTM D5185 measurement 1184 1192 1183 1212 S (% mass) ASTM D2622 measurement 3,342 (= Sinitial) 3,529 (= Sfinal) 3,519 (= Sfinal) 3,554 (= Sfinal) Bagtive at 150 ° C (% by weight), ASTM D1662 measurement 1,307 (= Initial Sactive) 1,245 (= Final Sacrifice) 1,174 (= Final Sacrifice) 1,145 (= Final Sacrifice) S / P (measured) 28.2 29.6 29.7 29.3 Sactif / S (measured) 0.39 0.35 0.33 0.32 Theoretical S (% mass) 3,530 3,560 3,540 Theoretical bag (% mass) 1,452 1,347 1,390 Final Sactif / Initial Sactif 0,952 0.898 0.876 Final S / Sinitial 1,056 1,053 1,063 Nature Function Reference A% by mass Phospho Souffré additive Additive Package of Performances 13.25 Poly Iso Butene Synthetic Thickener 5.50 polyacrylate Point-of-flow step 0.40 Bright Stock Solvent Viscous base 25.50 600 Neutral extracted Solvents Medium base 40.35 Di-isodecyl Adipate Basis of Synthesis 15,00

Chipping resistance tests:

• palier 10
• 90°C
• Engrenages de type C
• vitesse 1450 tours/minute
• Durée de vie mesurée : durée avant apparition d'écailles dont la surface totale couvre 5mm² ou plus sur l'engrenage

The chipping resistance tests were carried out on an FZG machine (machine identical to those used in the standardized tests DIN 51354 and CEC L07-A-95), under the following operating conditions, adapted to the evaluation of the phenomenon of chipping:

• tier 10
• 90 ° C
• Type C gears
• speed 1450 rpm
• Measured life: duration before appearance of scales whose total surface covers 5mm ² or more on the gear

The oils A, B, C and D were tested three times. The result is reported in the number of hours required to obtain a flaked surface of 5% in the test. The results of these tests are summarized in Table 4.

The relatively large dispersion of the tests is quite typical of chipping resistance tests, since this kind of wear occurs after a long aging time, preceding the sudden visible failures.

The improvement values observed for the various oils show a definite improvement for formulas B and D. However, it should be noted that the improvement obtained for oil B corresponds to a single trial of significant duration, the other two tests remaining a moderate improvement value.

The results obtained with the oil D are all at values much higher than those observed with reference A. This formula is therefore the most effective in the field of resistance to chipping. Table 4 formulas reference except invention invention invention AT VS B D % mass treatment rate 0.63% 1% 0.46% added active sulfur% mass 0.14% 0.04% 0.08% life time in hours test 1 42 84 56 98 test 2 56 28 126 70 test 3 28 56 56 98 average 42 56 79 89 standard deviation 14 28 40 16

Results interpretation :

It is found that in the range of values of the S / P ratio considered (between 25 and 35), the lifetime of the gears observed on the FZG peeling test is strongly correlated with the value of the ratio S / S and at the active sulfur content S. (correlation coefficient R ² = 0.92 and 0.99).

On the other hand, by comparing the theoretical and measured active sulfur contents for oils B, C, and D, the measured values are significantly lower than the theoretical values.

The addition of the compounds OS1, OS2, OS3 to the reference formula A effectively has the effect of lowering the active sulfur content in these formulas, with a concomitant increase in the lifetime of the gears observed on the test. flaking FZG.

Claims (10)

1. Use of a lubricating composition as a lubricant for increasing resistance to spalling of metal frictional parts, said lubricating composition comprising:

   (a) from 60 to 90 % by weight of one or more base oils, of mineral, synthetic or natural origin,

   (b) at least one anti-wear and extreme pressure phosphorous or sulfur-phosphorous additive,

   (c) 0.1 to 2% by weight of at least one anti-wear and extreme pressure sulfur-containing additive (c), said additive (c) is selected from one or more sulfurized olefins fitting the general formula R1-Sx-R2, wherein R1 and R2 are alkyl groups including from 3 to 15 carbon atoms and x is an integer comprised between 2 and 6 and said sulfur-containing additive (c) has a ratio between the active sulfur mass content at 150°C, as measured according to the ASTM D1662 standard, and the elementary sulfur mass content, as measured according to the ASTM D5185 standard, SactivelS, less than 0.45 and an elementary sulfur mass content, as measured according to the ASTM D5185 standard, larger than 20%, and wherein:

   - the ratio between the elementary sulfur mass content, as measured according to the ASTM D2622 standard, and the elementary phosphorus mass content, as measured according to the ASTM D5185 standard, S/P, of said lubricating composition, is comprised between 20 and 40, preferably between 25 and 35;

   - the ratio between the active sulfur mass content at 150°C, as measured according to the ASTM D1662 standard, and the elementary sulfur mass content, as measured according to the ASTM D5185 standard, SactivelS, of said lubricating composition, is less than 0.34, preferentially less than 0.33.
2. Use according to claim 1, wherein the lubricating composition has an active sulfur mass content at 150°C, Sactive, as measured according to the ASTM D1662 standard, less than or equal to 1.200 %, preferentially less than or equal to 1.180%.
3. Use according to claim 1 or 2, wherein the sulfur-containing additive (c) has an elementary sulfur mass content, as measured according to the ASTM D5185 standard, larger than 40 %.
4. Use according to any one of claims 1 to 3, wherein the lubricating composition comprises as a base oil (a), from 10 to 20% of one or more Group V base oils, optionally in combination with one or more base oils selected from the Groups I, II, III, IV or VI of the API classification, and/or base oils of natural origin.
5. Use according to any one of claims 1 to 4, wherein the 60 to 90% of base oil (a) are made up with:

   - 20 to 30 % by weight, relatively to the total weight of lubricant, of a paraffinic base oil of strong viscosity, belonging to the Group I of the API classification, with a viscosity comprised between 30 and 34 cSt at 100°C

   - 30 to 45 % by weight, relatively to the total weight of lubricant, of a Group I paraffinic base oil with a viscosity comprised between 10 and 15 cSt at 100°C

   - 10 to 20 % by weight, relatively to the total weight of lubricant, of a Group V synthetic oil.
6. Use according to any one of claims 1 to 5, wherein the anti-wear and extreme pressure phosphorous or sulfur-phosphorous additive(s) (b) are selected from alkyl phosphates, alkyl phosphonate, thiophosphoric acid, thiophosphorous acid, esters of these acids, their salts, alkyl dithiophosphates.
7. Use according to any one of claims 1 to 6, wherein the dynamic Brookfield viscosity of the lubricating composition is less than or equal to 150 mPa at temperatures above or equal to -12°C, preferentially above or equal to -26 °C, preferentially above or equal to -40° C.
8. Use according to any one of claims 1 to 7, wherein the kinematic viscosity of at 100°C of the lubricating composition is less than or equal to 32.5 cSt.
9. Use according to any one of claims 1 to 8, wherein the lubricating composition belongs to the class of multigrade oils of grades 85W140, 85W90, 80W90, or 75W90 or monograde oils of grade 140 or 90 according to the SAEJ306 standard.
10. Use according to any one of claims 1 to 9, wherein the metal frictional parts are gears of axles of vehicles.